[PATCH v8 3/5] loop: Add support for provision requests

Sarthak Kukreti
2023-10-07T01:28:44Z

Add support for provision requests to loopback devices.
Loop devices will configure provision support based on
whether the underlying block device/file can support
the provision request and upon receiving a provision bio,
will map it to the backing device/storage. For loop devices
over files, a REQ_OP_PROVISION request will translate to
an fallocate mode 0 call on the backing file.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
drivers/block/loop.c | 34 +++++++++++++++++++++++++++++++---
1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 9f2d412fc560..abb4dddbd4fd 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -311,16 +311,20 @@ static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos,
{
/*
* We use fallocate to manipulate the space mappings used by the image
- * a.k.a. discard/zerorange.
+ * a.k.a. discard/provision/zerorange.
*/
struct file *file = lo->lo_backing_file;
int ret;

- mode |= FALLOC_FL_KEEP_SIZE;
+ if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE) &&
+ !bdev_max_discard_sectors(lo->lo_device))
+ return -EOPNOTSUPP;

- if (!bdev_max_discard_sectors(lo->lo_device))
+ if (mode == 0 && !bdev_max_provision_sectors(lo->lo_device))
return -EOPNOTSUPP;

+ mode |= FALLOC_FL_KEEP_SIZE;
+
ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
return -EIO;
@@ -488,6 +492,8 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
FALLOC_FL_PUNCH_HOLE);
case REQ_OP_DISCARD:
return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
+ case REQ_OP_PROVISION:
+ return lo_fallocate(lo, rq, pos, 0);
case REQ_OP_WRITE:
if (cmd->use_aio)
return lo_rw_aio(lo, cmd, pos, ITER_SOURCE);
@@ -754,6 +760,25 @@ static void loop_sysfs_exit(struct loop_device *lo)
&loop_attribute_group);
}

+static void loop_config_provision(struct loop_device *lo)
+{
+ struct file *file = lo->lo_backing_file;
+ struct inode *inode = file->f_mapping->host;
+
+ /*
+ * If the backing device is a block device, mirror its provisioning
+ * capability.
+ */
+ if (S_ISBLK(inode->i_mode)) {
+ blk_queue_max_provision_sectors(lo->lo_queue,
+ bdev_max_provision_sectors(I_BDEV(inode)));
+ } else if (file->f_op->fallocate) {
+ blk_queue_max_provision_sectors(lo->lo_queue, UINT_MAX >> 9);
+ } else {
+ blk_queue_max_provision_sectors(lo->lo_queue, 0);
+ }
+}
+
static void loop_config_discard(struct loop_device *lo)
{
struct file *file = lo->lo_backing_file;
@@ -1092,6 +1117,7 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
blk_queue_io_min(lo->lo_queue, bsize);

loop_config_discard(lo);
+ loop_config_provision(lo);
loop_update_rotational(lo);
loop_update_dio(lo);
loop_sysfs_init(lo);
@@ -1304,6 +1330,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
}

loop_config_discard(lo);
+ loop_config_provision(lo);

/* update dio if lo_offset or transfer is changed */
__loop_update_dio(lo, lo->use_dio);
@@ -1857,6 +1884,7 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
case REQ_OP_FLUSH:
case REQ_OP_DISCARD:
case REQ_OP_WRITE_ZEROES:
+ case REQ_OP_PROVISION:
cmd->use_aio = false;
break;
default:
--
2.42.0.609.gbb76f46606-goog